This invention relates generally to a flexible polymeric membrane. More particularly, this invention relates to a flexible polymeric membrane for a roof or in other applications such as fluid containment liners and covers (e.g., reservoir and land fill liners and covers).
While the present invention will be described in connection with a roof application, it will be appreciated that the roof membrane disclosed herein may also be useful in other applications requiring heat weldable, water resistant, chemical resistant polymeric membranes.
In certain modern roofing installations for commercial buildings, a layer of insulation is secured to the deck of the roof and then is covered with sheets of flexible material. Adjacent margins of adjacent sheets are sealed together (e.g., heat welded) in overlapping relationship and thus the sheets form a sealing membrane over the insulation.
The sheets which form the membrane are secured to the insulation and the underlying roof deck at spaced locations by fastener assemblies which are spaced along the margins of the sheets. Each fastener assembly comprises a washer-like disc and further comprises a screw adapted to thread into the roof deck to cause the disc to clamp the membrane downwardly against the insulation.
A particularly successful single ply roofing material is based on synthetic rubbers made from chlorosulfonated polyethylenes (CSPE) such as HYPALON synthetic rubber made by E.I. DuPont DeNemours & Co. Chlorosulfonated polyethylenes exhibit excellent physical and chemical properties; and usually resist the deteriorating effects of ozone, oxygen, weather, heat and chemicals. CSPE is also easily processable into continuous sheets using conventional calendering equipment. As a result, CSPE is extremely well suited for use as a single ply roof and in other similar applications such as reservoir covers and land fill liners.
While well suited for its intended purposes, it has been determined that under certain severe environmental conditions with a high incidence of air pollution (i.e., produced by auto exhaust and similar industrial effluents), a roofing membrane based on chlorosulfonated polyethylenes may exhibit cracking. This is undesirable as it may result in the failure of the roof. Cracking is caused by pools of water (e.g., rain water) which collect on a roof. These pools contain a variety of pollutants. As the water in the pools evaporate, a viscous, sludge material is left behind. This viscous sludge is further transformed (under solar exposure) to a hard glassy structure similar to a dried varnish which adheres tightly to the roof. During the latter portion of this drying process, the hardened sludge shrinks with such shrinking process causing tears and cracks in the rubbery roof membrane.